Car Question -- Oiil Cap Popping Off?

Factual Questions
1

Here’s the story… My car has 13,000 miles on it. I had the oil changed at a quick change place at 10,000 miles.

Last week we had a big snowstorm, I had trouble backing out of the driveway, rocking back and forth, spinning my wheels, hitting into snowbanks. During the process I noticed there was some oil on the garage floor. After I got the car out of the driveway, it made the “loud muffler” sound whenerv I drove. I assumed that I had loosened part of the exhaust system while plowing backwards into the snow. I drove the car for a couple of days.

On Sunday, I checked the oil, and guess what… 1) There was NO oil on the dipstick, 2) There was NO oil cap on the engine.

I had the car towed to the dealer, there is no engine damage, everything is going to be OK, but one thing keeps me wondering… How did the oil cap come off?

The obvious explanation was that “someone” left it off. The obvious suspect is myself. However, I did not even check my oil since the last oil change. And if the quick change place left the cap loose at 10,000 miles, how come it took until now for it to come off? Did revving my engine in the snow have something to do with it?

And a further question is… Can I make a reasonable claim that this should be covered under my warranty, or under the extended warranty that I purchased? Can the oil cap just pop off by itself?

2

p.s., the “low oil” light never came on, why was that?

3

No oil on the dipstick doesn’t necessarily mean no oil in the engine. The end of the dipstick could be as close as 1/2 qt. below the low end of the “OK” zone. Presumably the engine still had a fair amount of oil in it, and the level wasn’t low enough to cause a warning light to come on.

The obvious explanation was that “someone” left it off.

Yes.

The obvious suspect is myself.

Why?

However, I did not even check my oil since the last oil change.

That seems to make the obvious suspect the folks who changed the oil.

And if the quick change place left the cap loose at 10,000 miles, how come it took until now for it to come off?

First of all, unless you specifically remember seeing the oil cap still on after the oil change, we have no way of knowing when it came off, or if it was even on the car when you left the oil change place. Secondly, if something like that is loose, it’s not possible to predict when it would vibrate off. It could take a short time or a long time.

Did revving my engine in the snow have something to do with it?

It may well have. The pattern of engine vibration while doing that might have been different from what occurs during your normal driving, and could have been what made it shake itself from loose to off.

Can I make a reasonable claim that this should be covered under my warranty, or under the extended warranty that I purchased? Can the oil cap just pop off by itself?

I don’t think a warranty claim would be considered (though it might be laughed at). On a car that new, it would be virtually impossible for a properly installed oil cap to just pop off. Human error is by far the more logical explanation.

4

Whilst ramming the snowbank, you made a nice snow “cork” in your tailpipe. Resulting in too much back pressure.

An amusing thought at least. How to make the leap from exhaust to oil cap/dipstick is an interesting path, and involves more than just a little havoc inside your engine. Then again, the backpressure may have caused a series of events that caused positive pressure to build up in the oil case. The cap still gets me though.

On second thought, the cheapo oil change place having an employee who is a space case is far more likely. With out an oil cap, oil tends to spray up and out of the cap (When the cap is of, your engine certainly makes a bit of noise. Sort of like a low groan.) That oil pools up on the manifold, and then down onto the floor. Some would burn up as well. Have you smelled anything? To blow off a dipstick, you would need a short, sharp, burst of pressure, not a slow build up. I just don’t see it.

5

ratatoskK, you didn’t say what kind of car you have, but yes, cars do have oil pressure under the cap & a cap that’s not tight could reasonably come off if there is enough pressure to push it…why don’t you get a new cap & tighten it & check it in a week or two & see if its still tight?

6

It’s a 2002 Toyota Camry. It’s at the dealer being fixed (they’ll put on a new cap, etc.). And I am DEFINITELY going to regularly check the cap from now on!!!

7

Its actually not a low oil light, it is more correct called a low oil pressure light.

Why didn’t it go on? As you mentioned, your engine is OK so presumebly the pressure didn’t get low enough to trip the light. This is a good thing.

Rule of thumb - If the oil light actually goes on, you’ve got problems on the way.

8

Don’t depend on a warning light like ‘oil pressure’ to detect low oil levels.

When the cap is replaced correctly, if it is secured correctly after each change, it will probably never come off again.

It was probably twisted half way on and the tension forced it out. If it was put on all the way, tension would have forced it back on.